Air cargo is a vital component of many international logistic networks, essential to managing and controlling the flow of goods and other resources from the source of production to the marketplace. For air cargo transportation, as well passenger aircrafts and cargo aircrafts are used. A passenger aircraft comprises a lower deck for the air cargo which is available under the passenger's main deck. A pure cargo aircraft (also known as freight aircraft, freighter, airlifter, or cargo jet) is an aircraft that is designed or converted for the carriage of goods, rather than for passengers. In cargo aircrafts the main deck as well as the lower deck is used to carry cargo.
In modern cargo aircraft, cargo may be loaded through hinged cargo doors located in a side of the fuselage. For loading the cargo aircraft, specially designed ULDs (unit load devices) are used. ULDs are containers or pallets which are used to load luggage, freight and other products into the cargo compartment of an aircraft. It allows a large quantity of cargo to be bundled into a single unit. Since this leads to fewer units to load, it saves ground crew's time and effort.
During loading, the ULDs are transferred into the fuselage through the hinged cargo door and are then maneuvered on the cargo deck which for this purpose comprises a cargo loading system. The cargo loading system typically consists of a plurality of uni- or multi-directional transfer supports to ease the passage of ULDs over the surface of the cargo deck and into a final stowed position where it is secured to the cargo deck against movements by a number of either fixed or relocatable restraints. The function of these restraints, which hereinafter are referred to as end stop devices, is to prevent movement of the cargo during operation, i.e. during takeoff, flight and landing. During operation, the ULDs are resting against these end stop means.
There are multiple different types of end stop devices used in an aircraft depending on the type of the cargo loading system. Examples of such end stop devices are described in EP 921 072 A2 and EP 104 946 B1.
Typical end stop devices available in the art are movable and fixable along corresponding seat track profiles or rails which are provided in the cargo deck surface. During operation, the complete cargo within the cargo deck is typically secured by some few end stop devices which consequently have to take up very high forces and loads. Therefore, a specific requirement of end stop devices is their capability to take very high loads without breaking. If an end stop device breaks under stress e.g. due to heavy loads, the seat track profiles would rip apart. Since this scenario necessarily has to be avoided, commonly known end stop arrangements have a rather massive construction. Massive construction, however, means additional weight and costs.